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If a hemiacetal is deprotonated at its hydroxyl group, what is the correct name for the resulting anion (or salt)?
I could not find anything, and assume that these compounds are probably not stable (just like most hemiacetals themselves), but I'd still be interested what's the right nomenclature here - something with -ate, -alkoxide, or the like?
Hemiacetals can actually be named as ‘hemiacetal’ using functional class nomenclature, e.g. pentanal ethyl hemiacetal. However, the preferred IUPAC names are generated using the usual systematic substitutive nomenclature, i.e. as substituted hydroxy compounds, e.g. 1-ethoxypentan-1-ol. The corresponding rules in the current version of Nomenclature of Organic Chemistry – IUPAC Recommendations and Preferred Names 2013 (Blue Book) read as follows.
P-66.6.5.2 Hemiacetals and hemiketals
Compounds with the general structure $\ce{RR'C(OH)(O-R'')}$ have the class name ‘hemiacetals’. They are named substitutively as ‘alkoxy’, ‘alkyloxy’, ‘aryloxy’, etc. derivatives of an appropriate hydroxy parent compound, such as an alcohol; these names are the preferred IUPAC names. Other names are formed by functional class nomenclature using the class name ‘hemiacetal’; similarly derivatives of ketones are denoted by the class name ‘hemiketal’.
According to P-72.2.2.2.2, an anion formed by subtracting $\ce{H+}$ from a hydroxy compound that can be expressed by a suffix ‘ol’ is systematically named by using compound suffix ‘olate’, formed by addition of the ending ‘ate’ to the suffix ‘ol’.
P-72.2.2.2.2 Anions derived from hydroxy compounds
An anion formed by subtracting a hydron from the chalcogen atom of a hydroxy characteristic group, or a chalcogen analogue, that can be expressed by a suffix such as ‘ol’, ‘thiol’, ‘-peroxol’, etc., is preferably named by using suffixes ‘alate’, ‘thiolate’, ‘peroxolate’, etc., formed by addition of the ending ‘ate’ to the suffixes ‘ol’, ‘thiol’, ‘peroxol’, etc. The multiplying prefixes ‘bis’, ‘tris’, etc. are used before these suffixes, to avoid any ambiguity.
(…)
Disappointingly, the current IUPAC recommendations still retain traditional names as preferred IUPAC names for anions of several simple alcohols (such as ‘ethoxide’ instead of the systematic name ‘ethanolate’).
The anion of my example 1-ethoxypentan-1-ol, however, is not affected by such exceptions; the systematic name 1-ethoxypentan-1-olate is also the preferred IUPAC name.
